"xpyttl" wrote

Presumably you are aware that a USB interface implies computation on both
sides. The relatively recent USB PICs (18F2550, 4550, etc.) incorporate
everything needed for the USB interface except the connector. Only a
couple
of years ago a USB controller chip was $26 and it needed a host of
additional parts to actually implement the interface. A smaller USB PIC
costs less than $5 and includes *everything*.

Go to http://ww1.microchip.com/downloads/e...Doc/39632D.pdf and take
a
look at the capabilities. To see it in an actual circuit, try
http://www.microchip.com/stellent/id...ame =en529760
and download the users guide. The 2550 is the little TQFP to the right of
the board picture, although it is available in a variety of packages, some
more hobbyist-friendly then the tiny one on the board. The only
additional part is an inductor to filter the USB voltage when it is used
to power the target circuit.

This series of parts also includes A/D channels, tho they might not be the
speed and resolution you want. The particular board is a nice one for
experimenting because it includes one of the fast 16-bit parts that are
easily programmable in a high level language, along with the USB
interface.



Many thnaks for the heads-up on the PICs. I've always tried to avoid USB
interfaces for control applications, but I have a project on the horizon
where I will almost certainly go down that route - simply because laptops no
longer have RS-232 ports..